The general objective of this work is to provide additional data to permit satisfactory cleansing of the hard clam Mercenaria mercenaria, taken from polluted waters. Satisfactory bacterial depuration can be obtained through most of the year if initial scores are less than 10 to the 3rd power, but, in our laboratory, bacteriophages at low levels are not eliminated by the clam. Clam-virus model studies are now being extended and will include a variety of enteroviruses found in our estuaries. These studies will employ methods for enumeration of viruses at low levels in the hard clam that have been developed over the past year. In addition, to evaluate the magnitude of the viral depuration problem, virus levels in naturally-contaminated hard clams from our polluted estuaries will be determined throughout the year.